Which mechanism most commonly leads to an MCL injury?

Which mechanism most commonly leads to an MCL injury?

• A. Direct trauma to the lateral knee with valgus force and rotation
• B. Direct trauma to the medial knee with varus force
• C. Hyperextension injury without valgus
• D. Axial loading through the tibia

Answer: (A)

The key idea is that the MCL is stressed by valgus stress on the knee, often with some external rotation of the tibia. A blow to the lateral side of the knee pushes the knee inward (valgus), placing tension on the medial collateral ligament as it tries to prevent abduction of the tibia. That’s why direct trauma to the lateral knee with valgus force and rotation best explains an MCL injury. A direct blow to the medial knee with varus force would load the lateral structures (lateral collateral ligament and related tissues) rather than the MCL. Hyperextension without valgus generally injures the ACL and posterior structures more than the MCL. Axial loading through the tibia stresses the joint surfaces and can cause tibial plateau or other injuries rather than targeting the MCL specifically.

The key idea is that the MCL is stressed by valgus stress on the knee, often with some external rotation of the tibia. A blow to the lateral side of the knee pushes the knee inward (valgus), placing tension on the medial collateral ligament as it tries to prevent abduction of the tibia. That’s why direct trauma to the lateral knee with valgus force and rotation best explains an MCL injury.

A direct blow to the medial knee with varus force would load the lateral structures (lateral collateral ligament and related tissues) rather than the MCL. Hyperextension without valgus generally injures the ACL and posterior structures more than the MCL. Axial loading through the tibia stresses the joint surfaces and can cause tibial plateau or other injuries rather than targeting the MCL specifically.